The present invention related generally to automotive service equipment adapted for the servicing of vehicles and vehicle components, such as vehicle wheel alignment systems, vehicle wheel balancing systems, vehicle tire changing systems, and vehicle brake testing systems, and specifically to automotive service equipment utilizing imaging technology to accurately measure distances, dimensions, and characteristics when servicing vehicles or vehicle components.
Conventional optical imaging technology utilizes an image sensor or camera to acquire a two-dimensional image of a target object. The two-dimensional image is typically composed of an array of image pixels, with each pixel having a value associated therewith corresponding to optical energy received at a discrete location on the image sensor or camera. Processing of the resulting two-dimensional image may be utilized to acquire accurate measurements of a target object in two dimensions, i.e. along the X-axis and Y-axis, but typically provides only limited information associated with a third dimension, i.e. along the Z- or distance axis.
Recent advances in three-dimensional imaging technology enable distance measurements along the Z-axis to be acquired for each pixel received in a two-dimensional image. For example, this technology is demonstrated by enabling virtual keyboard layouts to be projected onto any flat surface. The keyboard pattern is optimized for usability, featuring wide key spacing to improve typing accuracy, shortcut keys for popular applications, and adjustable brightness levels. The system includes a three-dimensional imaging sensor disposed behind a suitable lens which is configured to detect light projected from an infrared light source reflecting off a user's fingers as virtual keys are pressed. Associated software objects for controlling and utilizing data acquired by the three-dimensional imaging sensor is available for a wide variety of conventional personal computer and PDA operating systems. Data acquired by the three-dimensional imaging sensor is communicated to a host computer in a conventional manner, such as via either an RS-232 communications port or a USB interface.
Three-dimensional imaging technology provides the ability to accurately measure distances along a Z axis between the sensor and a target object, as well as provide conventional two-dimensional X and Y coordinates for features of a target object. Currently, sensors utilizing three-dimensional imaging technology locate objects in three-dimensional space at a rate of up to, or exceeding, 30 frames per seconds (fps). The three-dimensional imaging sensors require optical energy of a known wavelength to be reflected off the target objects undergoing three-dimensional imaging. All of the image processing to identify each pixel composing an image in an X, Y, and Z coordinate system is done in a logic circuit associated with the sensor element.
To measure the distance of a target object from a camera or sensor using Time Of Flight (TOF) three dimensional imaging, optical energy is directed towards the target object, and is correspondingly reflected from the target object back to the camera or sensor along individual pathways. The TOF for optical energy traveling along a first pathway is different than the TOF for optical energy traveling along other pathways. Additional information which can be accurately acquired from the camera or sensor utilizing an array of sensing elements includes placement of the target object along the X and Y axis of a three-dimensional coordinate system.
Alternative methods of determining dimensions of an object in an image are known in addition to the TOF three-dimensional imaging technology described above. For example, it is known to examine luminosity data from the reflection of optical energy off the target object. Pixels composing a resulting two-dimensional image which are darker are presumed to be further away than lighter pixels.
Structured light may be utilized to acquire distance measurements to a target object. A planar light beam may be directed towards the target object along a highly accurate and known angle. The light received from the associated reflections off the target can be used in conjunction with the known angle to determine a distance from receiver to target by using trigonometry. This method has been shown in vehicle service system applications in U.S. Pat. No. 5,054,918 to Downing et al. for “Light Scanning System For Measurement of Orientation and Physical Features Of A Workpiece.”
Acoustical measurement is commonly used in many applications today. The use of acoustical measurement in combination with a vehicle wheel balancing system is illustrated in U.S. Pat. No. 5,189,912 to Quinlan et al. for “Ultrasonic Wheel Measuring Apparatus and Wheel Balancer Incorporating Same.”
Yet another method to determine x, y, z dimensions from objects in an image is to use a technique like that used in machine vision vehicle wheel alignment sensors. Machine vision vehicle wheel alignment sensors are configured with a predetermined optical target containing several points in known locations which is manufactured with an extremely high degree of accuracy. An image of the target in three-dimensional space is acquired by a camera system. A mathematical duplicate of the target is then constructed to correspond to the acquired image, by solving spatial positioning equations have six unknown variables. These variables include displacement within an X, Y, and Z coordinate system, and the yaw, pitch, and roll of the target within the coordinate system. Because the relationship between points on the target surfaces are known to a high degree of accuracy, the mathematical duplication of the target identifies the position and orientation of the target in three dimensional space relative to the observing camera.
It is further known to utilize two or more imaging sensors to acquire stereoscopic images of a target object from which positional and dimensional information may be acquired. However, the stereoscopic approach is complicated because multiple imaging sensors or cameras are used to gather distance information instead of one imaging sensor. In a stereoscopic system, each imaging sensor or camera consists of an imaging element, a means to control the imaging element, and a means to communicate acquired images from the imaging element to a processing means where the images are processed to determine distances from the imaging sensors to the target object. A lens assembly is optionally included between the imaging element and the target object to improve the reception of optical energy reflected from the target object. Similarly, an optical energy source or emitter means may be provided to improve illumination of the target object.
Accordingly, it would be advantageous to provide an improved vehicle wheel service device, such as a vehicle wheel balancing system or a vehicle tire mounting system which is configured with one or more imaging sensors to acquire dimensional information associated with a vehicle or vehicle component undergoing service, and to utilize the acquired dimensional information to assist in completing a vehicle wheel service procedure.
For example, conventional vehicle wheel balancer systems perform a calculation known in the trade as “plane separation” which separates sensed vibrations into discrete imbalance masses disposed in two separate planes of a vehicle wheel assembly, consisting of a wheel rim and a tire. These planes are typically axial planes corresponding to the wheel rim edges (i.e., the placement location of clip-on imbalance correction weights), but can also be planes located between the wheel rim edges (i.e., the placement location for adhesive weights). In order to calculate proper imbalance correction weight sizes, the axial location and radial location of the planes must be known. The “plane separation” calculations are described in further detail in U.S. Pat. Nos. 2,731,834, 3,076,342, and 3,102,429.
Known methods to measure the parameters of a vehicle wheel rim for purposes of identifying the axial and radial location of imbalance correction weight placement planes include the use of manual calipers, mechanical arms connected to sensors, such as shown in U.S. Pat. Nos. 4,939,941, 4,341,119, 4,576,044, and 3,741,016, acoustical measurement techniques, such as shown in U.S. Pat. No. 5,189,912, and the use of structured light, such as shown in U.S. Pat. No. 5,054,918.
The imbalance correction weights used on today's wheel balancers include clip-on imbalance correction weights that are clipped onto the edge of a wheel rim, adhesive imbalance correction weights which are located axially inward from an edge of the wheel rim and adhered on an inside exposed surface of the wheel, and adhesive patch imbalance correction weights commonly used to correct large imbalances and which are located on an inner surface of the tire. Commonly, these options are presented to an operator on a display screen, requiring the operator to manually inspect the vehicle wheel rim to determine which type of imbalance correction weight is most appropriate.
Accordingly, it would be advantageous to provide an improved vehicle wheel service device, such as a vehicle wheel balancing system or a vehicle tire mounting system which is configured with one or more imaging sensors to acquire information associated with a vehicle wheel undergoing service, and to utilize the acquired information to assist in identifying suitable imbalance correction weight placement planes and imbalance correction weight types for a vehicle wheel undergoing an imbalance correction procedure.
During vibration reduction procedures for a vehicle wheel assembly, it is often necessary to measure the radial runout present in the surfaces on a wheel rim against which a tire is seated, i.e. the tire bead seat surfaces. For a wheel assembly having a wheel rim constructed from steel, it is often adequate to measure the radial runout of the inboard and outboard tire bead seats on the corresponding outer edges of the wheel rim because the steel wheel rim is formed in a single process which establishes a good correlation between the outer edges and the bead seat surfaces. However, for a wheel assembly having a wheel rim constructed from an alloy, the outer edges of the wheel rim and the bead seat surfaces are often formed during different machining steps. Variations can occur in radial runout between the outer edges and the bead seats surfaces. Hence, for alloy wheel rims a direct measurement of the inside bead seat surfaces provide the most accurate measure of radial runout.
With conventional vehicle wheel balancer systems measurement of an inner surface of the bead seats on a wheel rim requires a tedious and time consuming process. First, the wheel assembly must be removed from the vehicle wheel balancer system. Next, the tire is removed from the wheel rim using a vehicle tire changing system, the wheel rim (without the tire present) is remounted on the vehicle wheel balancer system, and radial runout at the bead seat surfaces is measured. The wheel rim is then removed from the vehicle wheel balancer system, and returned to the vehicle tire changing system, wherein the tire is remounted to the wheel rim matching a measured first harmonic high spot of the tire with an average first harmonic low spot of the wheel rim to decrease vibration in the wheel. Finally, the complete wheel assembly is again returned to the vehicle wheel balancing system to complete the balancing process utilizing the acquired bead seat radial runout information.
Accordingly, it would be advantageous to provide an improved vehicle wheel balancing system with a means to acquire bead seat radial runout information from the inner surfaces of a wheel rim bead seat without requiring complete removal and disassembly of the vehicle wheel assembly from the vehicle wheel balancing system.